The present disclosure relates generally to antennas and, in particular, to wave guide polarizers for antennas. Still more particularly, the present disclosure relates to circular polarizers for antennas.
A phased array antenna is a group of antennas in which the relative phases of the respective signals feeding the antennas may be varied in a way that the effect of a radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions. In other words, one or more beams may be generated that may be pointed in or steered into different directions. A beam pointing in a transmitting or receiving phased array antenna is achieved by controlling the phasing timing of the transmitted or received signal from each antenna element in the array.
The individual radiated signals are combined to form the constructive and destructive interference patterns of the array. A phased array antenna may be used to point one or more fixed beams or to scan one or more beams rapidly in azimuth or elevation.
Each antenna element in a phased array antenna may employ a polarizer. This polarizer converts a signal in a circular polarized form to a linearly polarized form or vice versa. Signals that are transmitted from an antenna may be converted from a linear polarized form to a circular polarized form for transmission. The conversion for an array receiving a signal is converted from circular to linear polarization. This conversion can be accomplished by these same devices. Further discussion is limited to the transmit case for brevity but inversely (conversion from circular to linear) also applies for the receive case. A polarizer may be placed within a waveguide and may be formed using different dielectric materials.
It is desirable to transform a linear polarized signal in a circular waveguide into a circular polarized signal in a manner with low loss, good matching, and a good fit within the cross section of the waveguide. Existing solutions for polarizers may involve a non-circular cross section in the waveguide to obtain the desired polarization of signals. These types of waveguides may require expensive manufacturing techniques. Further, these types of polarizers also may be more difficult to match.